1. Field of the Invention
The present invention relates to an integrated circuit package.
2. Background Information
Integrated circuits are typically incorporated into packages that are soldered to a printed circuit board. There has been developed various types of integrated circuit packages including quad flat pack (QFP), ball grid array (BGA) and controlled collapsed chip connect (C4) packages. C4 packages include a plurality of solder bumps that interconnect the integrated circuit to a substrate. The integrated circuit may also be enclosed by an encapsulant. The substrate can be attached to a circuit board such as the motherboard of a computer.
During operation, the integrated circuit generates heat which raises the temperature of the package. Conversely, when power to the integrated circuit is terminated the temperature of the package returns to an ambient level. This thermal cycle causes the integrated circuit and the substrate to both expand and contract.
This expansion creates stresses in the substrate. The stresses can create cracks in the substrate surface and which may cause electrical connectivity problems if these cracks propagate through the underlying metal traces. Many C4 packages include an epoxy underfill material that surrounds the solder bumps. The underfill material is typically dispensed along one side of the integrated circuit and then flows between the circuit and the substrate under capillary forces. It is desirable to completely fill the space between the integrated circuit and the substrate with underfill material without having the material flow to an undesirable area of the package. It would be desirable to provide a feature in the integrated circuit package that will contain the underfill material during the dispensing process.